Audi Q5: General Information
High pressure side are the condenser, receiver/dryer and restrictor or expansion valve to separate the high and low pressure liquid ends.
High pressure results from the restrictor or expansion valve forming a constriction and causing the refrigerant to accumulate, thus leading to an increase in pressure and temperature.
Excess pressure occurs if too much refrigerant or refrigerant oil is used, the condenser is contaminated, the radiator fan is malfunctioning, the system is blocked or there is moisture in the refrigerant circuit (icing-up of restrictor or expansion valve).
Low pressure side are the evaporator, reservoir, evaporator temperature sensor and A/C compressor to separate high and low pressure gas ends.
A drop in system pressure can be caused by loss of refrigerant, the restrictor or expansion valve (no constriction), a malfunctioning A/C compressor or an iced-up evaporator.
Mechanically Driven A/C Compressor
The A/C compressor is driven by a ribbed belt or a input shaft, which is driven by the vehicle engine.
A/C Compressor with A/C Clutch
- An electromagnetic clutch -A- attached to A/C compressor provides the power link between the ribbed belt pulley -B- and A/C compressor crankshaft with A/C system switched on.
- An overload safeguard attached to the clutch plate or in the A/C compressor solenoid coil is tripped if the compressor does not move freely, thus protecting the belt drive against overload.
A/C Compressor without A/C Clutch
- An overload safeguard attached to the pulley of the compressor -B- is tripped if the compressor does not move freely, thus protecting the belt drive against overload.
All A/C Clutch
The A/C compressor extracts the refrigerant gas from the evaporator, compresses it and relays it to the condenser.
Note
- The A/C compressor contains refrigerant oil, which can be mixed with refrigerant R134a under any temperature.
- The data plate lists the type of refrigerant required for the A/C compressor. A regulator valve regulates pressure within the specified range (control characteristics) on the low pressure side.
- A/C compressors with or without an A/C clutch are currently controlled externally by a regulator valve -C-.
- On A/C compressors without an A/C clutch, the engine is only to be started following complete assembly of the refrigerant circuit.
- So that the A/C compressor does not get damaged when the refrigerant circuit is empty, the A/C clutch is turned off and the A/C Compressor Regulator Valve -N280- is no longer activated (A/C compressor runs at idle with engine).
- If the refrigerant circuit is empty, a A/C compressor without A/C Clutch -N25- with (A/C Compressor Regulator Valve -N280-) is switched to internal lubrication by way of a valve.
- Depending on the A/C compressor version, there may be a valve installed on the high pressure side of the A/C compressor, which prevents the liquid refrigerant from flowing back into the compressor once the A/C is turned off. If an A/C compressor with this valve is installed in a vehicle with a refrigerant circuit having an expansion valve, then it may take some time until the pressure in the high pressure side decreases (the expansion is cold and the pressure in the low pressure side quickly increases after it is turned off, the expansion valve closes and the refrigerant flows slowly into the low pressure side). If the A/C compressor is switched on, the pressure on the low pressure side goes down, the expansion valve open and the refrigerant can flow of the low pressure side.
- The electromagnetic clutch -A- is activated only when the regulator valve -C- is activated on an A/C compressor with an electromagnetic clutch -A- and with a regulator valve -C-. Refer to → Heating, Ventilation and Air Conditioning; Rep. Gr.87; System Overview - Refrigerant Circuit.
